1. Field of the Invention
The present invention relates to a cutting insert mounted on a replaceable insert turning tool and capable of reliably disposing of cutting chips produced under various cutting conditions from a medium cutting for cutting relatively a large amount to a light cutting such as a finish cutting for cutting a small amount.
2. Description of the Related Art
Such a cutting insert capable of reliably disposing of cutting chips produced under various cutting conditions from the medium cutting to the finish cutting is discussed in, for example, Japanese Unexamined Patent Application, First Publication No. 2006-272548. In the cutting insert, a breaker groove is formed along a cutting edge on a rake face. A protrusion of a boss surface extends to a corner portion of the cutting edge. The tip of the protrusion shows a concave shape surrounding the corner portion as seen from a plane. A standing face protruding to be longest near the cutting edge from two top portions of the protrusion showing the concave shape is formed. The standing angle of the corner is 10 to 30 degrees. The standing face is formed farther than the cutting edge as it is distanced from the corner portion.
However, the cutting insert described in Japanese Unexamined Patent Application, First Publication No. 2006-272548, the standing face protrudes from two top portions of the protrusion to the rake face near the cutting edge. Thus, it is difficult to form the aforementioned standing angle since a gradient of the standing face is steep based on a protrusion height of the top portion of the protrusion and a distance from the top portion to the cutting edge. Accordingly, in the medium cutting for cutting relatively large amount, the standing face is prematurely abraded by contacting with cutting chips, and there is concern that durability of the insert is deteriorated. On the other hand, when the protrusion height of the top portion of the protrusion is set small in order to make the standing angle be in the range, the cutting chips produced in the process of the finish cutting for cutting small amount overflow out of the protrusion. As a result, it is difficult to smoothly dispose of the cutting chips.
The present invention has been made in consideration of the aforementioned situations, and has an object of providing a cutting insert capable of reliably disposing of cutting chips even in a finish cutting and having long durability even in a medium cutting.